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Legolaz
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The Dance In Microwaves

10/12/2015 12:30 AM

Hello,

I knew that microwave oven disturb molecular kinetics of water and produces heat as a consequent. My question is, does heating water produces microwave signals even in minute amplitude?

Thank you.

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SolarEagle
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#1

Re: The dance in microwaves

10/12/2015 1:30 AM

No I don't think so, the microwave energy is transferred to the water as heat, and the heat dissipates to the surrounding materials that are cooler through conduction and convection and radiation, the radiation is around the infrared wavelength, microwave would be a little higher....

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JWthetech
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#4
In reply to #1

Re: The dance in microwaves

10/12/2015 7:59 AM

Ah GA but backwards, microwave (RF) is at least an order of magnitude below infrared
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dj95401
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#2

Re: The dance in microwaves

10/12/2015 1:32 AM

Depends on what your heat source is to heat the water. Did you happen to ask Google for their opinion ?

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Rixter
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#3

Re: The dance in microwaves

10/12/2015 7:16 AM

No. If the heating of the water were due to a resonance of the water molecule, as commonly believed, it might be possible for some increased radiation of microwaves at that frequency. Microwave absorption in water is broadband. The microwave frequency chosen for microwave ovens is to provide the proper penetration depth. Too short a wavelength would only heat the food on the surface. The 2.5 GHz frequency is a compromise that allows sufficient absoption to heat the food, yet allows penetration to the center.

http://www.schoolphysics.co.uk/age16-19/Wave%2520properties/Wave%20properties/text/Microwave_ovens/index.html
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#5

Re: The Dance In Microwaves

10/12/2015 8:08 AM

Actually the answer is both yes and no.

On the one hand, everything above absolute zero is radiating some energy all across the electromagnetic spectrum which includes emitting microwaves at some level. (And everything is also absorbing energy in the same way, thus remaining at thermal equilibrium with its surroundings.)

So yes, heating water in any manner will increase the amount of energy it emits, which would include an increased amount of microwave energy. Even when the heat source is taken away it will continue to emit more energy than it receives, until it is again in thermal equilibrium with its surroundings.

(Look up 'black body radiator' or 'Planck's Law'.)

But No, it won't emit just microwave energy, if that's what you're wondering.

(There are devices which can be stimulated to emit at specific microwave wavelengths. They are called masers, and were the precursors to lasers.)

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redfred
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#6
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Re: The Dance In Microwaves

10/12/2015 9:44 AM

GA

The only thing I wish to emphasize is that the vast majority of photon frequencies emitted by liquid water being heated to a boil at sea level will be many decades lower than the microwave band. However a very, very small fraction of the emittance will be in the microwave band. The frequency of the peak of this emittance distribution can tell how hot is that body.

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Legolaz
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#7
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Re: The Dance In Microwaves

10/13/2015 2:42 AM

So, what makes water sensitive to the wavelength of microwave? Does the natural frequency of water molecules in line with microwave length?

I thought it must be, since only water is heated, plastics and glass does not otherwise. Water could be a good antenna for microwave at that aspect, but only that water is poor conductor. Do you agree?

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redfred
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#8
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Re: The Dance In Microwaves

10/13/2015 8:10 AM

That's a complicated question to properly answer. The first thing you have to recognize is that water has a very high dipole moment, the oxygen atom has the electrons. Also the hydrogen atoms are about 120° apart from each other thus a more positive and a more negative part of this neutrally charged molecule exists.

Once you grasp this concept you cane then understand an article on water absorption spectra. If you are ambitious you can read the scholarly articles on water and microwave absorption spectra.

There is also Wikipedia article, too. They present some very good animations on the vibrational and rotational kinematics of this molecule. This is what makes water such a good translator of microwave energy into thermal energy.

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Legolaz
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#9
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Re: The Dance In Microwaves

10/14/2015 12:28 AM

Awesome!

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JWthetech
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#10
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Re: The Dance In Microwaves

10/14/2015 9:25 AM

Both plastic and glass are heated in a microwave oven. There are several spectacular Youtube videos of beer bottles in a microwave.
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dj95401 (1); JWthetech (2); Legolaz (2); redfred (2); Rixter (1); SolarEagle (1); Usbport (1)

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